back to article Prof: Use wind turbines as flywheels to smooth output

A team of Wisconsin-based academic engineers have come up with a novel idea for smoothing out wind turbines' erratic power output in gusty conditions. In essence, the Milwaukee team's idea is to use the turbine itself as a giant flywheel to siphon off energy spikes and so offer more consistent output. The research was led by …


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  1. Danny

    big giant gusts?

    This sounds like a bad idea to me. The amount of KE stored in those flywheels will be rather high. Lets hope they can feather the props pretty quickly...

  2. Emo

    Why not

    Fit them with an internal flywheel with a clutch to engage and disengage it as and when needed?

  3. Anonymous Coward
    Anonymous Coward

    Reduced max output

    If they are going to use the higher speed to store the energy as a flywheel then this must reduce the maximum output of the wind turbine. They cant use the higher rotational speeds for both generating maximum output and for storage as kinetic energy.

  4. Ian Rogers
    Thumb Down

    Air resistance

    Not really a flyer (heh). The blades are made of a quite light material compared to the amount of drag they experience in still air so would come to a standstill after only a few 10s of seconds at most.

    They'd also need a constant variable transmission gearbox to enable the blades to turn faster for a constant output frequency. Currently turbine blades feather to keep a constant rotation speed.

  5. Andus McCoatover

    Yeah, we see one..

    When "Her Indoors" (actually me indoors - she's employed, I ain't) and I go out to the balcony for a smoke in the morning, we can see a Great Big Fuc*Koff Wind Turbine about a kilometre away. There's at least 4 more lesser ones in sight, however, spinning like tops.

    I think the former GBFOWT is for test purposes (, perhaps- it's on a place I'm not allowed to go to) because over the last couple of months it hasn't done much apart from turn it's "head" into the wind. Even when we had a serious gale a week ago, it'd rotate no faster than usual.

    Q. Which politican said "I got one of those roof-mounted windy-thingies. Got rid of it soon after. Cost a bleeding fortune in 'leccy keeping the sodding thing spinning on a calm day"? Peter "Avocado Mousse" Mandelson?

  6. Anonymous Coward
    Anonymous Coward

    Academics huh ?

    So in essence the idea is to rate windmills at only 75% of peak speed so that as they coast back down they still hit rated output ?

    Clever people can be so stupid sometimes.

  7. Anonymous Coward
    Anonymous Coward

    Academic engineers??????

    I was going to ask what they were but realised they were the 'engineers' that I used to clean up for - after all the big cockups they made.

    As several people have said there are real world problems with the proposed idea, the least of which is the fact the turbines are very carefully designed NOT to over speed for several reasons - like the blade tips breaking the sound barrier and the problems that would bring.

    All those 'Academic engineers' should be forced to work out in industry for at least five years before they can call themselves Engineers! Maybe there would then be more sense coming from the universities.

  8. Steven Jones

    day long calms

    "It seems unlikely that this technique would be able to cope with the days-long calms which some critics of wind power have pointed out"

    Understatement of the year, and it has barely started. In still conditions, the air resistance will bring the turbine to a stop in a few minutes, even if the blades could be feathered. This is clearly just designed to even out short term speed variations and get more power during gusty periods.

  9. Dave


    Nice to see this article, so shortly after seeing stories about the turbine that was largely destroyed by a UFO.

    (Most critical minds seem to think that it went over-speed, leading to some nice, circular flames, before throwing one and a half blades clean off the hub.) And that was under normal circumstances, without deliberately trying to make it run faster than normal.

    <- Flames, 'cos there will be plenty more if this idea is even tested, let alone mass-produced.

  10. Anonymous Coward

    @ Dave

    Dave It wasn't windy enough for overspeed!

    however if the antiicing failed on that blade it was cold enough for enough ice to destabilise the hub and cause enough vibration to break the blade root. which could have colided with the second blade or a shock vibration could also have ruptured the bonding of the two blade halves.

    (watch the danish vid in slo-mo and see the second blade fails dus to shock vibrations)

  11. Anonymous Coward

    Daft... but...

    Blades as flywheels is daft due to extra weight, greater loads more expensive towers, wind resistance etc, however there is a long tower which would be ideal for a hanging shaft type flywheel, I would advise an electric coupling/transmission for optimum control. No change to the turbine head they work just fine.

  12. RichardB

    Potential energy

    How about putting together a load of weights and pulleys - surely lifting a couple of tons up over time would do the trick - like the old clocks. When the wind stops the weight would keep it spinning.

  13. Terry

    @ Ivan

    That's the worst idea I've ever heard. In 5 years these fools could destroy civilization! How about we just put them in a cave for 5 years. Their ramblings are probably a tremendous source of global warming anyhow.

    BTW, you're in charge of remembering to let them out in 5 years. If you're unavailable I'll do it.


    Honest. No, really... I'm sure I'll remember. I'll put it in my Vista Calendar.

  14. John Sager

    Not designed for the purpose

    Turbines don't make good flywheels, and a proper engineer would either know that, or be able work it out in a couple of minutes on the back of an envelope. A better solution would be to build a flywheel storage unit specially designed for the purpose for each wind farm. With the appropriate control electronics that would be able to peak-lop short-term (a few minutes) wind variations, and more easily match the offered capacity to the trading pool, but no way will it buffer longer term variations (winter highs like we have ATM).

  15. Richard Kay
    Thumb Up

    day long calms

    Are better dealt with by uprating hydro electric facilities:

  16. Ed Blackshaw Silver badge

    Surely a better idea

    would be to have some sort of arrangement as follows:

    prop -> clutch -> flywheel <-> turbine <-> grid

    so that when wind blows, the blades drive the flywheel which drives the turbine, but when no wind blows the blades disengage while the flywheel spins?

    Just make sure that the failure mode of the clutch is to engage, or you get the video that was posted here yesterday of the blade tips hitting the sound barrier and exploding...

  17. Colin Millar

    Simple things

    Why go to the bother of making some complex mechanical thingy designed for a specific purpose even more complex to fulfil another specific purpose?

    Why not just design another mechanical thingy that does the other specific purpose?

  18. Andrew Steer


    Having a big heavy flywheel at the top of a tower seems fundamentally bad, but given that the rotor is typically free to turn to face the wind, you really don't want the flywheel up there. The top would be liable to shear off when the wind changes direction.

    Surely this interpretation isn't what is proposed?

  19. Anonymous Coward

    Use Wind Turbines as UAV/UFO catchers?

    Lewis, what's your take on the suggestion that a "Taranis" UAV hit that Lincolnshire wind turbine?

  20. Don Mitchell

    Fly-Wheel Storage

    Using a seperate fly wheel to store energy from a wind turbine has been done too. The Russian aeronautical engineers, Vetchinkin and Ufimtsev built a prototype in 1914.

  21. m-s-m


    Most large turbines will rotate at a more or less constant speed, changing the pitch of the blades according to the current wind speed, that's why it won't rotate faster in a gale.

  22. Anonymous Coward

    Lots of posters trolled by Lewis' Aunt Sally re "days-long calms"..

    Oh dear. A whole lot of chips are showing on a whole lot of shoulders here.

    Although the actual paper is unavailable, there are a number of other articles easily googleable, and if you do a bit of reading it quickly becomes clear that all these guys are claiming to have invented is

    "a novel control method that can mitigate power fluctuations using the inertia of the wind turbine's rotor as an energy storage component. Simply put, they have created a braking control algorithm that adjusts the rotor speed so that when incoming wind power is greater than the average power, the rotor is allowed to speed up so that it can store the excess energy as kinetic energy rather than generating electricity. This energy is then released when the wind power falls below average."

    It's not supposed to deal with day-long calms and they never claimed it did.

    It's a minor incremental improvement to the behaviour of the system, and it has the advantage that it can be done by modifying the braking control software of existing systems *without* the need for expensive hardware modifications such as installing flywheels or banks of capacitors. That's why it's clever and useful

    It only involves modulation of the rotor speed, it's still a fully controlled process that's not going to over-spin unless something breaks, so it's not really any different in that regard than how the turbines operate already anyway.

    So all the people dismissing it because of the supposed day-long-calm or over-speed issues are probably coming at it from a prejudged conlusion based on a "I hate all that tree-hugging hippy shit" attitude rather than a reasoned assessment of the actual claims being made for it...

  23. Sillyfellow

    no title

    good reading.

    another thought.. put a big heavy flywheel on the windmills so that next time a UFO crashes into one...

  24. Steve

    Re: Industry engineers

    If everything that academia thought of worked perfectly straight away, there would be no industrial engineers.

    Maybe we should leave theory and research to industrial engineers. How many A-frames and how much 4by6 would it take to put a man on the moon?

  25. David Pollard

    @ Sillyfellow

    What's required is more education and training for the ETs, so that they tether their spaceships to wind turbines without crashing. They can then plug into the grid to provide backup power, as they won't be using interstellar drive while parked.

  26. Erik Aamot

    @ Potential energy

    rather than weights and pulleys ..

    when the grid does not need the elecricity , you use the turbine to pump water uphill to a reservoir .. when the turbines are idle or more electricity is needed for the grid during peak usage .. you run the water back downhill with gravity thru efficient hydroelectric generation

    in combination with water holding tanks at wind turbine level, it can be a closed system where fresh water use might not present a problem except in quite arid areas

    this is what T. Pickens had planned in Texas and north along the east side of the Rockies, where wind is relatively consistant .. other than dropping oil prices have delayed development and there are significant water use issues in Texas

    given significant enough scope, such reservoirs of stored energy could last for days and at least give buffer if conventional generation needed to be put back online in extended calm periods

    frankly though, the windfarm idea all falls apart as a commercial / profitable venture if you were to rely on much more than about 10% of peak need .. this might translate to 20% more average need, however you'd still need 90% conventional peak capacity, used less efficiently ( and therefore less profitably ) to handle usage peaks, or ramp back industry use during peak periods, again introducing economic inefficiencies

    true figure might be less efficiency and reliabilty in Europe vs US eastern Rockies ..

    we've had windfarms in California for decades, about 13,000 units producing 30% of the world's total of electricity from wind .. and guess what ? ..

    a whopping 1.5% of California's electrical power is wind power.. and inconsistant at that

    waste biomass manages 2.6% .. geothermal does 4.5 % .. hydroelectric 14.5% .. nuclear nearly 13% of electrical generation .. all relatively consistant and managable with changing demand

    it's easy to see that waste biomass generation and nuclear have much greater potencial than wind power to replace any significant percentage of gas / oil / coal use

  27. foo_bar_baz

    @all sceptics

    Amusing how all these experts are so eager to dismiss the proposed technology and take the opportunity to piss on their favourite target, academics in this case. How dare anyone think different? You'd all be stoning heretics or ridiculing heliocentrism had you been born a few centuries ago. OTOH the article set you up for it. Glad the AC put the record straight.

  28. Tom Oliva

    Pretty Good - but.....

    Given that UK electrons are four times more expensive than French electrons and more than twice as expensive as German electrons - you'd think that they'd have a bit of cash spare and just install some pilot plants to see how well it works...

    As I understand it flywheel storage has been around for a few years (French telephone giant Alcatel I believe uses it for exchange standby) and, as I understand it works pretty well and is dirt cheap to implement with bugger all maintenace.

    UK utilities aren't keen to open the doors to "devolved power" as it opens Pandora's Box as far as distributed generation goes. Heavens above !! - can't have people generating their own power and heating their houses with the waste heat.....

    UK utilities are by and large, delinquent bureaucracies - whose prime raison d'etre has SFA to do with supplying the population with reasonably priced electrons.

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